The pwgen program is designed to be used both interactively, and in shell scripts. Hence, its default behavior is differs depending on whether the standard output is a tty device or a pipe to another program. Used interactively, pwgen will display a screenful of passwords, allowing the user to pick a single password, and then quickly erase the screen. This prevents someone from being able to "shoulder-surf" the user's chosen password.

When standard output is not a tty, pwgen will only generate one password, as this tends to be much more convenient for shell scripts, and in order to be compatible with previous versions of this program. In addition, for backwards compatibility reasons, pwgen will not use upper case letters or numbers by default in this mode, although this can be overridden using the -n and -c options.

-0, --no-numerals

Don't include numbers in the generated passwords.

-1

Print the generated passwords one per line.

-A, --no-capitalize

Don't bother to include any capital letters in the generated passwords.

-a, --alt-phonics

This option doesn't do anything special; it is present only for backwards compatibility.

-B, --ambiguous

Don't use characters that could be confused by the user when printed, such as 'l' and '1', or '0' or 'O'. This reduces the number of possible passwords significantly, and as such reduces the quality of the passwords. It may be useful for users who have bad vision, but in general use of this option is not recommended.

-c, --capitalize

Include at least one capital letter in the password. This is the default if the standard output is a tty device.

-C

Print the generated passwords in columns. This is the default if the standard output is a tty device.

-N, --num-passwords=num

Generate num passwords. This defaults to a screenful if passwords are printed by columns, and one password.

-n, --numerals

Include at least one number in the password. This is the default if the standard output is a tty device.

-H, --sha1=/path/to/file[#seed]

Will use the sha1's hash of given file and the optional seed to create password. It will allow you to compute the same password later, if you remember the file, seed, and pwgen's options used. ie: pwgen -H ~/your_favorite.mp3#your@email.com gives a list of possibles passwords for your pop3 account, and you can ask this list again and again.

WARNING: The passwords generated using this option are not very random. If you use this option, make sure the attacker can not obtain a copy of the file. Also, note that the name of the file may be easily available from the ~/.history or ~/.bash_history file.

-h, --help

Print a help message.

-s, --secure

Generate completely random, hard-to-memorize passwords. These should only be used for machine passwords, since otherwise it's almost guaranteed that users will simply write the password on a piece of paper taped to the monitor...

-y, --symbols

Include at least one special character in the password.